Automatically shiftable transmissions require a supply of pressurized oil or fluid to operate. The pressurized fluid may be used for such functions as lubrication, torque converter operation, and engagement of torque transmitting mechanisms for gear ratio interchange. The fluid is typically stored in a main reservoir or main sump volume where it is introduced to a pickup or inlet tube for communication to a hydraulic pump. The hydraulic pump operates to pressurize the fluid for subsequent communication to components within the transmission. Therefore, the inlet tube must remain submerged in fluid during the operation of the transmission to avoid starvation of the hydraulic pump. To this end, an adequate fluid level or volume is typically maintained within the main sump volume of the transmission during cold operation. At higher fluid temperatures, the fluid tends to expand and entrain an amount of air such that the volume of fluid within the main sump volume may increase significantly.
At cold operating temperatures, an amount of fluid must be provided within the sump volume to provide the inlet tube with an uninterrupted flow of fluid during vehicular maneuvers, such as cornering and hard acceleration. This amount of fluid, referred to as the maneuver volume, is typically much greater than that which is required for steady state vehicular operation. To reduce the maneuver volume required during cold operation, while providing an uninterrupted flow of fluid to the inlet tube, engineers have developed dry sump systems, baffle systems, and sliding inlet tubes to name a few.